How much do I love axolotls? A whole lotl 😆!
Captive color morph axolotl, photo by th1098, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Axolotls only live in a very small area, and they are under environmental pressure that could wipe them out over time. Scientists have come together to save the axolotl, partly because they are a big part of their cave ecosystem, and partly because they want to keep these fascinating animals around to study them.
There’s certainly a lot that makes these creatures interesting! Their frilly external gills and permanent smile make them look cute and friendly. They have a fin that extends all the way down their back, and they suck down their food like little vacuum cleaners.
But there’s also a trait that has grabbed the attention of the science world: regeneration. Axolotls can regenerate lost body parts, huge patches of skin, internal organs, and their spinal cords. 😱
Axolotls aren’t alone in their ability to regrow limbs. Starfish can grow back arms, and chameleons can grow back tails. The axolotl grows back arms and legs so perfectly, though, that they completely repair nervous, skeletal, and muscle tissue. Experts are wondering: how do the axolotl cells know what to do?
There have been some recent discoveries in regeneration that shed some light on this question. Scientists have learned that a key player in the regeneration of limbs is a chemical called retinoic acid. Retinoic acid levels start off high in regenerating limbs. As cell growth reaches the end of the limb, enzymes break the acid down. The missing retinoic acid tells the new tissue to stop growing.
Even more exciting, it turns out cancer is extremely rare in the axolotl. Scientists think its ability to regenerate might have something to do with resisting cancer. Scientists don't have all the answers yet, but hopefully, in the future, all this information can be used to help human medicine.
One thing scientists have learned is that the superhero traits of axolotls start to slow down as the animal ages. Check out the graph below to see how limb regrowth compares between young and old axolotls.
If I brought this graph into the classroom, here are some questions I'd have to go with it:
💡How long does it take the larval axolotl to completely grow back a limb? How do you know?
💡How many days did it take for the larval axolotl to regrow 20% of its limb compared to the adult axolotl?
💡What percent of their limb has the larval axolotl grown after 40 days? What about the adult axolotl? Why might scientists be interested in this information?